Differences in cardiac activation times for endocardium and epicardium response to external electric shock

摘要

Externally applied electric shocks, E{sub}a, which are used to terminate cardiac defibrillation, operate by altering the cardiac transmembrane potential through a mechanism that is not yet understood. The effect of E{sub}a on endocardium andepicardium was studied on Langendorff-perfused, di-4-ANEPPS stained isolated rabbit right ventricles (RV) to which a 10-40 V/cm E{sub}a was applied from plate electrodes inside a Tyrode's bath. Field stimulation of the flat RV preparation caused immediate distributed depolarization followed by rapid, non-propagative activation of the entire RV wall. For every E{sub}a strength tested, the activation time, T{sub}a, of the epicardium was shorter than epicardial T{sub}a. This difference in T{sub}a may beattributed to a higher degree of anatomical heterogeneities on the endocardial surface.